【转帖】神经网络电活动增强快速调控抑制性突触稳态可塑性的分子机制

The Journal of Neuroscience doi:10.1523/JNEUROSCI.3085-10.2010

Postsynaptic Spiking Homeostatically Induces Cell-Autonomous Regulation of Inhibitory Inputs via Retrograde Signaling

Yi-Rong Peng,1,2 * Si-Yu Zeng,1,2 * He-Ling Song,1 Min-Yin Li,1,2 Maki K. Yamada,3,4 and Xiang Yu1

1Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China, 2Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China, 3PRESTO (Precursory Research for Embryonic Science and Technology), Japan Science and Technology Agency, Saitama 332-0012, Japan, and 4Department of Cellular Neurobiology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan

Correspondence should be addressed to Xiang Yu at the above address. Email: yuxiang@ion.ac.cn

Developing neural circuits face the dual challenge of growing in an activity-induced fashion and maintaining stability through homeostatic mechanisms. Compared to our understanding of homeostatic regulation of excitatory synapses, relatively little is known about the mechanism mediating homeostatic plasticity of inhibitory synapses, especially that following activity elevation. Here, we found that elevating neuronal activity in cultured hippocampal neurons for 4 h significantly increased the frequency and amplitude of mIPSCs, before detectable change at excitatory synapses. Consistently, we observed increases in presynaptic and postsynaptic proteins of GABAergic synapses, including GAD65, vGAT, and GABAAR1. By suppressing activity-induced increase of neuronal firing with expression of the inward rectifier potassium channel Kir2.1 in individual neurons, we showed that elevation in postsynaptic spiking activity is required for activity-dependent increase in the frequency and amplitude of mIPSCs. Importantly, directly elevating spiking in individual postsynaptic neurons, by capsaicin activation of overexpressed TRPV1 channels, was sufficient to induce increased mIPSC amplitude and frequency, mimicking the effect of elevated neuronal activity. Downregulating BDNF expression in the postsynaptic neuron or its extracellular scavenging prevented activity-induced increase in mIPSC frequency, consistent with a role of BDNF-dependent retrograde signaling in this process. Finally, elevating activity in vivo by kainate injection increased both mIPSC amplitude and frequency in CA1 pyramidal neurons. Thus, spiking-induced, cell-autonomous upregulation of GABAergic synaptic inputs, through retrograde BDNF signaling, represents an early adaptive response of neural circuits to elevated network activity.